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• FFmpeg/libav : YUV420P to RGB conversion

  17 janvier 2014, par learner

  I am working with Video encoding-decoding based on online tutorials. In the encoding section, the dummy image created is in YUV420P format. I need it to be in RGB or BGR format. Any idea how to do this ??

   #include 
  
   #include 
  
   #include 
  
  
  
   #ifdef HAVE_AV_CONFIG_H
  
   #undef HAVE_AV_CONFIG_H
  
   #endif
  
  
  
   #include "libavcodec/avcodec.h"
  
   #include "libavutil/mathematics.h"
  
  
  
   #define INBUF_SIZE 4096
  
   #define AUDIO_INBUF_SIZE 20480
  
   #define AUDIO_REFILL_THRESH 4096
  
  
  
   /*
  
   * Video encoding example
  
   */
  
   static void video_encode_example(const char *filename)
  
   {
  
       AVCodec *codec;
  
       AVCodecContext *c = NULL;
  
       int i, out_size, size, x, y, outbuf_size;
  
       FILE *f;
  
       AVFrame *picture;
  
       uint8_t *outbuf, *picture_buf;
  
  
  
       printf("Video encoding\n");
  
  
  
       /* find the mpeg1 video encoder */
  
       codec = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);
  
       if (!codec)
  
       {
  
           fprintf(stderr, "codec not found\n");
  
           exit(1);
  
       }
  
  
  
       c = avcodec_alloc_context();
  
       picture = avcodec_alloc_frame();
  
  
  
       /* put sample parameters */
  
       c->bit_rate = 400000;
  
       /* resolution must be a multiple of two */
  
       c->width = 352;
  
       c->height = 288;
  
       /* frames per second */
  
       c->time_base= (AVRational){1,25};
  
       c->gop_size = 10; /* emit one intra frame every ten frames */
  
       c->max_b_frames=1;
  
       c->pix_fmt = PIX_FMT_YUV420P;
  
  
  
       /* open it */
  
       if (avcodec_open(c, codec) < 0)
  
       {
  
           fprintf(stderr, "could not open codec\n");
  
           exit(1);
  
       }
  
  
  
       f = fopen(filename, "wb");
  
       if (!f)
  
       {
  
           fprintf(stderr, "could not open file! %s\n", filename);
  
           exit(1);
  
       }
  
  
  
       /* alloc image and output buffer */
  
       outbuf_size = 100000;
  
       outbuf = malloc(outbuf_size);
  
       size = c->width * c->height;
  
       picture_buf = malloc((size * 3) / 2); /* size for YUV 420 */
  
  
  
       picture->data[0] = picture_buf;
  
       picture->data[1] = picture->data[0] + size;
  
       picture->data[2] = picture->data[1] + size / 4;
  
       picture->linesize[0] = c->width;
  
       picture->linesize[1] = c->width / 2;
  
       picture->linesize[2] = c->width / 2;
  
  
  
       /* encode 1 second of video */
  
       for(i=0; i<25; i++)
  
       {
  
           fflush(stdout);
  
           /* prepare a dummy image */
  
           /* Y */
  
           for(y=0; y < c->height; y++)
  
           {
  
               for(x=0; x < c->width; x++)
  
               {
  
                   picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
  
               }
  
           }
  
  
  
           /* Cb and Cr */
  
           for(y=0; y < c->height/2; y++)
  
           {
  
               for(x=0; x < c->width/2; x++)
  
               {
  
                   picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
  
                   picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
  
               }
  
           }
  
  
  
           /* encode the image */
  
           out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);
  
           printf("encoding frame %3d (size=%5d)\n", i, out_size);
  
           fwrite(outbuf, 1, out_size, f);
  
       }
  
  
  
       /* get the delayed frames */
  
       for(; out_size; i++)
  
       {
  
           fflush(stdout);
  
  
  
           out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
  
           printf("write frame %3d (size=%5d)\n", i, out_size);
  
           fwrite(outbuf, 1, out_size, f);
  
       }
  
  
  
       /* add sequence end code to have a real mpeg file */
  
       outbuf[0] = 0x00;
  
       outbuf[1] = 0x00;
  
       outbuf[2] = 0x01;
  
       outbuf[3] = 0xb7;
  
       fwrite(outbuf, 1, 4, f);
  
       fclose(f);
  
       free(picture_buf);
  
       free(outbuf);
  
  
  
       avcodec_close(c);
  
       av_free(c);
  
       av_free(picture);
  
       printf("\n");
  
   }
  
  
  
   /*
  
    * Video decoding example
  
    */
  
  
  
   static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
  
                        char *filename)
  
   {
  
       FILE *f;
  
       int i;
  
  
  
       f=fopen(filename,"w");
  
       fprintf(f,"P5\n%d %d\n%d\n",xsize,ysize,255);
  
       for(i=0; i* set end of buffer to 0 (this ensures that no overreading happens for damaged mpeg streams) */
  
       memset(inbuf + INBUF_SIZE, 0, FF_INPUT_BUFFER_PADDING_SIZE);
  
  
  
       printf("Video decoding\n");
  
  
  
       /* find the mpeg1 video decoder */
  
       codec = avcodec_find_decoder(CODEC_ID_MPEG1VIDEO);
  
       if (!codec) {
  
           fprintf(stderr, "codec not found\n");
  
           exit(1);
  
       }
  
  
  
       c = avcodec_alloc_context();
  
       picture = avcodec_alloc_frame();
  
  
  
       if(codec->capabilities&CODEC_CAP_TRUNCATED)
  
           c->flags|= CODEC_FLAG_TRUNCATED; /* we do not send complete frames */
  
  
  
       /* For some codecs, such as msmpeg4 and mpeg4, width and height
  
          MUST be initialized there because this information is not
  
          available in the bitstream. */
  
  
  
       /* open it */
  
       if (avcodec_open(c, codec) < 0) {
  
           fprintf(stderr, "could not open codec\n");
  
           exit(1);
  
       }
  
  
  
       /* the codec gives us the frame size, in samples */
  
  
  
       f = fopen(filename, "rb");
  
       if (!f) {
  
           fprintf(stderr, "could not open file! %s\n", filename);
  
           exit(1);
  
       }
  
  
  
       frame = 0;
  
       for(;;) {
  
           avpkt.size = fread(inbuf, 1, INBUF_SIZE, f);
  
           if (avpkt.size == 0)
  
               break;
  
  
  
           /* NOTE1: some codecs are stream based (mpegvideo, mpegaudio)
  
              and this is the only method to use them because you cannot
  
              know the compressed data size before analysing it.
  
  
  
              BUT some other codecs (msmpeg4, mpeg4) are inherently frame
  
              based, so you must call them with all the data for one
  
              frame exactly. You must also initialize 'width' and
  
              'height' before initializing them. */
  
  
  
           /* NOTE2: some codecs allow the raw parameters (frame size,
  
              sample rate) to be changed at any frame. We handle this, so
  
              you should also take care of it */
  
  
  
           /* here, we use a stream based decoder (mpeg1video), so we
  
              feed decoder and see if it could decode a frame */
  
  
  
           avpkt.data = inbuf;
  
           while (avpkt.size > 0)
  
           {
  
               len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
  
               if (len < 0)
  
               {
  
                   fprintf(stderr, "Error while decoding frame %d\n", frame);
  
                   exit(1);
  
               }
  
               if (got_picture)
  
               {
  
                   printf("saving frame %3d\n", frame);
  
                   fflush(stdout);
  
  
  
                   /* the picture is allocated by the decoder. no need to
  
                      free it */
  
                   snprintf(buf, sizeof(buf), outfilename, frame);
  
                   pgm_save(picture->data[0], picture->linesize[0],
  
                            c->width, c->height, buf);
  
                   frame++;
  
               }
  
               avpkt.size -= len;
  
               avpkt.data += len;
  
           }
  
       }
  
  
  
       /* some codecs, such as MPEG, transmit the I and P frame with a
  
          latency of one frame. You must do the following to have a
  
          chance to get the last frame of the video */
  
  
  
       avpkt.data = NULL;
  
       avpkt.size = 0;
  
       len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
  
       if (got_picture)
  
       {
  
           printf("saving last frame %3d\n", frame);
  
           fflush(stdout);
  
  
  
           /* the picture is allocated by the decoder. no need to
  
              free it */
  
           snprintf(buf, sizeof(buf), outfilename, frame);
  
           pgm_save(picture->data[0], picture->linesize[0],
  
                    c->width, c->height, buf);
  
           frame++;
  
       }
  
  
  
       fclose(f);
  
  
  
       avcodec_close(c);
  
       av_free(c);
  
       av_free(picture);
  
       printf("\n");
  
   }
  
  
  
   int main(int argc, char **argv)
  
   {
  
       const char *filename;
  
  
  
       /* must be called before using avcodec lib */
  
       avcodec_init();
  
  
  
       /* register all the codecs */
  
       avcodec_register_all();
  
  
  
       if (argc <= 1)
  
       { 
  
           video_encode_example("asdf.mpg");
  
           filename = "asdf.mpg";
  
       }
  
       else
  
       {
  
           filename = argv[1];
  
       }
  
  
  
       video_decode_example("%d.pgm", filename);
  
  
  
       return 0;
  
  }

  I tried with PIX_FMT_RGB24 and changing each channel accordingly. For this, I declared another :

  AVFrame *pictureRGB ; and then : pictureRGB = avcodec_alloc_frame() ;

  for(y=0; y < c->height; y++)
  
  {
  
       for(x=0; x < c->width; x++)
  
       {
  
            pictureRGB ->data[0][y * pictureRGB ->linesize[0] + x] = x + y + i * 3;
  
            pictureRGB ->data[1][y * pictureRGB ->linesize[1] + x] = x + y + i * 3;
  
            pictureRGB ->data[2][y * pictureRGB ->linesize[2] + x] = x + y + i * 3;
  
       }
  
  }

  But it gives errors ! I am totally new to this library. Is it possible to directly encode as a RGB dummy image rather than as YUV420P. Anybody out there with sound knowledge in this area ??? Thanks in advance !

• python multiprocessing and ffmpeg corrupts files

  1er juillet 2012, par misterte

  I'm currently trying to convert several videos to three different outputs, all using ffmpeg : mp4, webm and jpeg. I also need to run this script in different directories and create within the directories webm, mp4 and jpeg subdirectories where the respective converted files are stored.

  I am running the following script inside a directory with 8 .mov test files in it. Files work ok as .mov.

  (It's a bit long, so here you can view it online)

  The script creates all files and directories. I can also note that all Consumer processes take tasks and complete them. The problem is resulting .mp4 and .webm files are corrupted.

  Here you can see an example output. It's a bit long, so I think it's best if I point out the part I think is relevant.

  ...
  
  [h264 @ 0x121815a00]no frame!
  
  Error while decoding stream #0.0
  
  [h264 @ 0x121815a00]AVC: nal size -6554108
  
  [h264 @ 0x121815a00]no frame!
  
  Error while decoding stream #0.0
  
  [h264 @ 0x121815a00]AVC: nal size 391580264
  
  [h264 @ 0x121815a00]no frame!
  
  ...

  This does not happen if I run ffmpeg straight from the console.

  ffmpeg -i movie.mov -b 500k -s 640x360 -padtop 60 -padbottom 60 movie_out.webm

  I can even run it in parallel shells and the output will not be affected.

  Can anyone see what the problem is ?

  thnx !

  A.

• How to combine a .mp4 video with a .wav audio with an offset in ffmpeg from command line ?

  15 mars 2014, par minder42

  I've got a TV clip in mp4 format containing audio and video, and an WAV audio_commentary track.

  I've been trying to combine them in ffmpeg and then play it online with a flash player (which can only take h264 format)

  What's the best ffmpeg command to accomplish this ? My inputs are MP4 video, WAV audio, and an offset in seconds, the time the audio commentary starts relative to the start of the mp4 video.

  I tried

  ffmpeg -i input_audio.wav -i input_vid.mp4 -vcodec copy output.mp4

  and

  ffmpeg -vcodec copy -ss offset -i input_audio.wav -i input_video.mp4 output.mp4

  nether of these do what I want and output the video in the h264 format that is good for flash players- Is there a way to do this from command line in ffmpeg ?